JPH11147379A - Film for heat-sensitive stencil printing, and heat-sensitive stencil printing master - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the piercing property by a thermal head at a low energy by a method wherein the D-lactic acid component amount in a thermoplastic resin which is used for a biaxially drawn film, is made a specified range. SOLUTION: For a polymer which is used for this film for heat-sensitive stencil printing, a polylactic acid is made the major component, and the D-lactic acid component amount in the polylactic acid is made 70 mol.% or higher. In this case, for the polymer with the polylactic acid as the major component, the D-lactic acid is made a major raw material, an L-lactic acid, and glycol acid, hydroxy butyric acid, hydroxy valeric acid, hydroxy carboxylic acids such as hydroxy caproic acid are jointly used, and the polymer with the polylactic acid as the major component is obtained by directly subjecting these raw materials to dehydration polycardenssation. Therefore, by making the D-lactic acid component amount 70 mol.% or higher, the piercing sensitivity in a low energy region can be improved, and at the same time, an unevenness of the pierced diameter can be reduced, and the printing property for character printing and solid printing or the like can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal head,
Alternatively, regarding a heat-sensitive stencil film and a heat-sensitive stencil master, which are perforated by a halogen lamp, a xenon lamp, a flash lamp, a laser beam, or the like,
Small variation in perforation diameter, excellent perforation sensitivity and printability,
In particular, the present invention relates to a film and a master excellent in perforation at a low energy by a thermal head.

[0002]

2. Description of the Related Art Conventionally, as a heat-sensitive stencil master, a vinylidene chloride film, a polyester film,
For thermoplastic resin films such as polypropylene film,
There is known a structure in which a porous support made of natural fiber, chemical fiber or synthetic fiber or a thin paper, nonwoven fabric, gauze or the like obtained by mixing them is bonded with an adhesive (for example, see Japanese Patent Application Laid-Open No. SHO 51-51). No. 2513, JP-A-57
182495).

However, recently, high resolution is required for printed materials. For example, in the case of perforation by a thermal head, in order to obtain a high resolution, each head is made smaller and the head heating cycle is shortened, so that perforation per unit area is performed. Attempts have been made to increase the number. Therefore, it is necessary to reduce the energy supplied to each head, and it is necessary that the above-mentioned thermoplastic resin film is sufficiently perforated with low energy.

[0004] Further, it is necessary that productivity and handleability during film production and master production be good. Specifically, it is necessary that the film has good stretchability, does not break during the film forming process, and has excellent winding properties and slit properties.

[0005] In order to solve such problems, a film in which the composition of the polymer used for the film is specified (Japanese Patent Application Laid-Open Nos. 2-158391 and 7-276839).
JP-A-62-282884, a film in which the thermal characteristics of a biaxially stretched polyester film are regulated.
JP-A-3-39294, JP-A-4-224925
And the like have been proposed.

[0006]

However, in the above-mentioned prior art, when drilling with low energy, the drilling is not sufficient, and the variation in the drilling diameter is large.
There are drawbacks such as poor printability such as solid printing.

[0007] The present invention solves the various problems of the prior art, and has a small variation in perforation diameter, is excellent in perforation sensitivity and printability, and is particularly excellent in heat-sensitive stencil printing having excellent low-energy perforation by a thermal head. The purpose is to provide films.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have focused on the functions of the heat-sensitive stencil printing film and the master, and the mechanism of perforation stencil making and printing, and have conducted intensive studies. In addition to the film made of lactic acid polymer, D-
The inventors have found that the drawbacks of the conventional film can be improved by obtaining a biaxially stretched film in which the amount of the lactic acid component is in a specific range, and have completed the present invention. That is, the present invention relates to a film for heat-sensitive stencil printing, which is a biaxially stretched film composed of a polymer mainly composed of polylactic acid, wherein the amount of the D-lactic acid component in the polylactic acid is 70 mol% or more. is there. Further, there is provided a heat-sensitive stencil master comprising a biaxially stretched film made of a polymer having a D-lactic acid component content of 70 mol% or more in polylactic acid and a porous support.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer used for the heat-sensitive stencil printing film of the present invention is mainly composed of polylactic acid, and the amount of the D-lactic acid component in the polylactic acid must be 70 mol% or more.
More preferably 80 mol% or more, even more preferably 90 mol% or more.
Mol% or more. Such polymers include D-
Lactic acid homopolymer, D-lactic acid / L-lactic acid copolymer, D
-Lactic acid / hydroxycarboxylic acid copolymers and mixtures thereof.

By setting the amount of the D-lactic acid component to 70 mol% or more, a film having excellent perforation sensitivity in a low energy region, small variation in perforation diameter, and excellent printability such as character printing and solid printing can be obtained. be able to.

The heat-sensitive stencil film of the present invention must be a biaxially stretched film. In an unstretched film, although it is melted at the time of perforation, it is difficult to form a hole, resulting in poor perforation sensitivity. In addition, since the strength of the film is low, printing durability is also poor.

In the heat-sensitive stencil film of the present invention, the effects of the present invention are more remarkably exhibited when the film thickness and the surface characteristics of the film, ie, the center line average roughness and the maximum roughness are within the ranges described below. preferable.

The thickness of the film of the present invention is preferably from 0.2 to 3.0 μm from the viewpoint of low energy perforation. Further, it is more preferably 0.3 to 2.5 μm, and further preferably 0.4 to 2.0 μm, from the viewpoint of film forming stability, handleability, and low energy perforation in film production.

The central average roughness (R) of the film of the present invention
a) is preferably in the range of 0.01 to 0.5 μm, and more preferably 0.05 to 0.4 μm in terms of stable productivity, perforation characteristics, and print clarity from the film formation to the master preparation step.

The maximum roughness (Rt) of the film of the present invention is:
The range is preferably 0.3 to 5 μm, and 0.5 to 4 μm from the viewpoint of film handling, productivity, and variation in perforation sensitivity.
μm is more preferred.

Further, the crystal melting energy [ΔHu] of the film of the present invention is 20 to 50 J / g from the viewpoint that the dimensional change due to the change in temperature and humidity is small, and the handleability and low energy perforation are good. And more preferably 30 to 40 J / g. The crystal melting temperature [Tm] of the film of the present invention is preferably 220 ° C. or lower, more preferably 200 ° C. or lower, and further preferably 180 ° C. or lower. It is preferable to set the crystal melting temperature to 220 ° C. or lower, because a molten portion serving as a starting point of perforation is easily formed and the perforation sensitivity is improved. In addition, due to the composition of the film being a blend, etc., if a shoulder is present or a plurality of peaks are present, it is preferable that at least the shoulder or peak on the lowest temperature side is in the above range, more preferably all. Is such that the shoulder or peak satisfies the above range.

The glass transition temperature of the film of the present invention [T
g] is preferably 50 to 120 ° C, more preferably 6 to 120 ° C.
0-110 ° C. Glass transition temperature of 50 to 120 ° C
This is preferable because the dimensional stability and the perforation sensitivity are improved.

The heat-sensitive stencil master of the present invention comprises a film and a porous support bonded to each other. The porous support is a porous substrate made of natural fiber, synthetic fiber, or the like that can transmit the printing ink and that does not substantially undergo thermal deformation under heating conditions under which the film is perforated. , Non-woven fabric, woven fabric, or other porous material.

The basis weight of the porous support bonded to the film of the present invention is preferably from 1 to 20 g / m ² from the viewpoint of printability. More preferably, it is ^{2 to} 16 g / m ² , still more preferably ² to 14 g / m ² . When the basis weight is 20 g / m ² or less, the ink permeability becomes good, and the printed image does not fade even when the printing speed is increased. When the basis weight is 1 g / m ² or more, it is possible to obtain an excellent master having good ink retention and a clear image.

The average diameter of the fibers constituting the porous support is preferably 0.5 to 30 μm, more preferably 1 to 20 μm, further preferably 1 to 10 μm, and particularly preferably 1 to 5 μm. When the average diameter is 30 μm or less, a master having uniform ink permeability can be obtained. When the average diameter is 0.5 μm or more, sufficient strength as a support can be obtained, so that the transportability becomes good.

Further, all the fibers constituting the porous support may have the same diameter, or fibers having different fiber diameters may be mixed. Further, a multilayer structure in which layers made of fibers having different fiber diameters are laminated stepwise may be used. In the case of a multilayer structure, at least the layer facing the film is composed of fibers of 10 μm or less, and the remaining layers are 10 μm or less.
It is more preferable to use fibers of not less than μm in terms of balance between image clarity and support strength. In the case of a multilayer structure, the basis weight of the fiber facing the film is more preferably 1 to 5 g / m ² . The film and master of the present invention can be produced by the following method.

The polymer mainly composed of polylactic acid in the present invention can be obtained by the following method. As a raw material, D-lactic acid can be mainly used, and L-lactic acid and a hydroxycarboxylic acid such as glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, or hydroxycaproic acid can be used in combination. In addition, these hydroxycarboxylic acid cyclic ester intermediates, for example, lactide, glycolide and the like can also be used as raw materials. Further, dicarboxylic acids, glycols and the like can also be used.

The polymer mainly composed of polylactic acid can be obtained by a method of directly dehydrating and polycondensing the above raw materials or a method of ring-opening polymerization of the above cyclic ester intermediate.
For example, when produced by direct dehydration polycondensation, lactic acids or lactic acids and hydroxycarboxylic acids are preferably subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether-based solvent, and particularly preferably azeotropically distilled. Polymerization by a method in which water is removed from the solvent to obtain a substantially anhydrous solvent and returned to the reaction system gives a polymer having a high molecular weight suitable for the present invention. The molecular weight of the polymer is preferably in the range of 10,000 to 1,000,000 from the viewpoint of moldability as a film.

In the polymer mainly composed of polylactic acid of the present invention, polyglycolic acid and polyglycolic acid containing a hydroxycarboxylic acid component as a constituent component can be used as long as the amount of the D-lactic acid component is within a range of 70 mol% or more. Butyric acid, polyhydroxybutyrate and the like, polyethylene terephthalate and polyethylene having a dicarboxylic acid component and a glycol component as constituents
2,6-naphthalate, polybutylene terephthalate,
Polyesters such as polyhexamethylene terephthalate, polyethylene isophthalate, polycyclohexane dimethylene terephthalate, and polybutylene succinate, or blends with copolymers mainly containing these polyesters may be used. In the case of a copolymer, it may be a random copolymer or a block copolymer.

The polymer mainly composed of polylactic acid in the present invention may contain, if necessary, a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a crystal nucleating agent, a pigment, a plasticizer, and a terminal. A blocking agent, an organic lubricant such as a fatty acid ester or a wax, or an antifoaming agent such as a polysiloxane can be blended. Furthermore, lubricity can be imparted according to the purpose. There is no particular limitation on the method of imparting lubricity,
For example, clay, mica, titanium oxide, calcium carbonate, calcium phosphate, kaolin, talc, alumina,
Examples include a method of blending inorganic particles such as zirconia, spinel, wet or dry silica, organic particles having acrylic acid-based polymers, polystyrene and the like as constituents, a method of applying a surfactant, and the like. The amount of the particles to be blended is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the polymer. The average diameter of the particles to be blended is preferably from 0.01 to 3 μm, more preferably from 0.1 to 2 μm. Such particles may be used in combination of plural kinds having different types and average diameters.

The film of the present invention is obtained by biaxially stretching the above-mentioned polymer. As the stretching method, inflation simultaneous biaxial stretching method, stenter simultaneous biaxial stretching method, is a biaxially stretched by any method of the stenter sequential biaxial stretching method, film forming stability,
From the viewpoint of thickness uniformity, a film formed by a stenter sequential biaxial stretching method is preferable.

The film of the present invention can be produced by using the above-mentioned polymer by the following method. After the polymer has been sufficiently dried, it is fed to an extruder for 15 minutes.
An unstretched film is obtained by melting at 0 to 300 ° C. and extruding onto a casting drum by a T-die extrusion method. As a method of adhesion to the casting drum, any method such as an electrostatic application method, an adhesion method using surface tension of water, an air knife method, a press roll method, etc. may be used, but the flatness is good and As a technique for obtaining a film having few surface defects, it is particularly preferable to use a contact casting method using surface tension of water or the like or an electrostatic application method. At this time, an unstretched film having a desired thickness can be produced by adjusting the slit width of the die, the discharge amount of the polymer used for the film, and the rotation speed of the casting drum. Next, a biaxially stretched film can be produced by simultaneously or sequentially biaxially stretching the unstretched film. In the case of sequential biaxial stretching,
The stretching order may be the order of the film in the longitudinal direction and the width direction, or vice versa. Further, in the sequential biaxial stretching, stretching in the longitudinal direction or the width direction can be performed twice or more. The stretching ratio in the longitudinal direction and the width direction of the film can be arbitrarily set according to the desired degree of orientation, strength, elastic modulus, etc. of the film. Preferably 2.0
It is up to 7.0 times. Either the stretching ratio in the longitudinal direction or the stretching direction in the width direction may be increased, and may be the same. The stretching temperature can be any temperature within the range from the glass transition temperature of the polymer used to the crystallization temperature. Further, after biaxially stretching the film, a heat treatment may be performed for the purpose of improving strength, stability over time, and shrinkage characteristics. This heat treatment can be performed by any method, such as in an oven or on a heated roll. The heat treatment temperature can be any temperature not lower than the stretching temperature and not higher than the melting point.
0 ° C. or less. The heat treatment time can be arbitrarily set, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. The heat-treated film may be rapidly cooled to a glass transition temperature or lower after the heat treatment, or may be cooled stepwise.

The heat-sensitive stencil master of the present invention can be prepared by bonding the above-mentioned film and a porous support.
The bonding between the film and the porous support may be performed using an adhesive or the like as long as it does not hinder the perforation suitability of the film. The method is more preferable because the transmission of the ink is not hindered by the adhesive or the like. More preferably, it is a method in which a non-woven fabric having a low orientation made of a thermoplastic resin is obtained by thermocompression bonding and co-stretching in a film production process. The unstretched film and the unstretched nonwoven fabric are integrally stretched in a thermocompression-bonded state, so that the nonwoven fabric serves as a reinforcing member, and has excellent curl resistance and printing durability. It is preferable because it is extremely excellent in stability. The method of co-stretching is not particularly limited, and is preferably the same as a film stretching method such as a stenter sequential biaxial stretching method.

The film and master of the present invention are subjected to an aging treatment for the purpose of reducing deformation such as dimensional change and curl due to changes in temperature and humidity during long-term storage in the manufacturing process as long as the effects of the present invention are not impaired. May be applied. The treatment is preferably performed at a treatment temperature of 30 to 80 ° C. for a treatment time of about 1 to 100 hours.

The fibers constituting the porous support may be subjected to a chemical treatment such as acid or alkali treatment, a corona treatment, a low-temperature plasma treatment or the like, if necessary, to impart an affinity to the ink. Good.

In the master of the present invention, it is preferable to apply a release agent to the film surface in order to prevent fusion with a thermal head or the like. As the release agent, silicone oil, silicone-based resin, fluorine-based resin, surfactant, wax-based release agent and the like can be used. In these release agents, various additives can be used in combination as long as the effects of the present invention are not impaired. For example, antistatic agents, heat-resistant agents, antioxidants, organic particles, inorganic particles, pigments and the like can be mentioned. The release agent may be applied at any stage before or after stretching the film. The application method is not particularly limited, but application is preferably performed using a roll coater, a gravure coater, a reverse coater, a bar coater, or the like. Also, if necessary before applying the release agent,
The surface to be coated may be subjected to a corona discharge treatment in air or other various atmospheres.

[Method for Measuring Characteristics] (1) Film Thickness A film sample was arbitrarily selected from ten locations, cut out in a cross-sectional direction, photographed with an electron microscope at a magnification of 2000 times, and the film thickness was measured. This was performed for 10 photographs, and the average value was shown.

(2) Crystal melting energy Differential scanning calorimeter RDC220 manufactured by Seiko Denshi Kogyo KK
Using a mold, sample a 5 mg film sample, cool it from room temperature to −50 ° C. in a nitrogen atmosphere, hold for 5 minutes,
The temperature was raised to 00 ° C. at a rate of 10 ° C./min to obtain a DSC curve. The crystal melting energy was determined from the peak area of the endothermic curve at this time. This area is shifted from the baseline to the heat absorption side by increasing the temperature, and is the area from which the temperature is further increased and returns to the baseline position. a)
Ask for. In (indium) was measured under the same DSC conditions, and the area (b) was determined as 28.5 J / g by the following equation.

Crystal melting energy = 28.5 × a / b (J / g) In the case where there are a plurality of peaks, each peak was determined and the sum was calculated.

(3) Perforation characteristics The created master was used as a RISOGR manufactured by Riso Kagaku Corporation.
The plate was supplied to the APH "GR275", and a plate made of JIS first-level black circles (circled in black) and having a diameter of 10 mm was prepared as originals by a thermal head plate making method (400 dpi). At this time, the energy input to the thermal head was 30 μJ per dot. Perforation was performed in this state, and 150 perforated portions of the film were observed with a scanning microscope at a magnification of 100 times, and the area of the perforated portion of the film was measured. The average value and standard deviation of the perforated area per dot were obtained, and the perforation characteristics were evaluated by the following items.
Both 感 度 and ○ are practically usable for both sensitivity and variation.

A. Perforation sensitivity A: Average perforation area of 1500 μm ² or more ○: Average perforation area of 1000 μm ² or more and 1500 μm ²
Less than Δ: Average perforated area is 500 μm ² or more and 1000 μm ²
Less than ×: The average perforated area is less than 500 μm ² .

B. Perforation variation Variation degree = 10 × log (average perforation area / standard deviation of perforation area) 2 ◎: Variation degree of 15 or more ○: Variation degree of 10 or more and less than 15 △: Variation degree of 5 or more Less than 10 ×: Less than 5 degree of variation.

(4) Print clarity Test chart NO. Using 8 as a document, a master prepared using a 400 dpi thermal head was made, a print sample was prepared with black ink, and the following characteristics were evaluated for characters and images (solid printing).
In both character printing and solid printing, ◎ and ○ are practically usable.

A. Clarity of character printing Character missing and thickness unevenness were visually observed and evaluated. ◎: No missing characters and non-uniform thickness at all ○: Missing characters and non-uniform thickness of 1 to less than 5 places △: Non-existent characters and non-uniform thickness of 5 to less than 10 places ×: Those with missing characters and uneven thickness more than 10 places.

B. Clarity of solid printing The solid black portion of the 100th printed matter printed using a plate-making original was measured and evaluated using a Macbeth optical densitometer. ◎: Concentration of 1.0 or more ：: Concentration of 0.9 or more and less than 1.0 Δ: Concentration of 0.8 or more and less than 0.9 ×: Concentration of less than 0.8.

[0041]

The present invention will be described below in more detail with reference to examples.

Example 1 100 parts by weight of D-lactic acid polymer A having a weight-average molecular weight of 170,000 having a composition ratio of D-lactic acid to L-lactic acid of 95: 5, 100 parts by weight of cohesive silica particles having an average particle size of 1.2 μm After adding and mixing 0.4 parts by weight, the mixture was supplied to a twin-screw extruder and extruded at 200 ° C. into pellets. The obtained pellets were dried at 120 ° C. under reduced pressure for 3 hours, and then extruded at a T-die die temperature of 210 ° C. using an extruder having a screw diameter of 45 mm to obtain a diameter of 300 m.
m to form an unstretched film. Then 3.5 mm in the longitudinal direction between heating rolls at 88 ° C.
After stretching twice, it is sent to a tenter type stretching machine, stretched 3.7 times in the width direction at 93 ° C, and further stretched at 100 ° C in a tenter.
To produce a 1.2 μm thick film.
The crystal melting energy of the film was 35.0 J / g.

Next, the obtained film was bonded to Japanese paper made of 100% natural fiber made of manila hemp using vinyl acetate as an adhesive and a fiber weight of 12 g / m ² , and a silicone release agent was applied to the film surface. Then, a heat-sensitive stencil master was prepared and evaluated. Table 1 shows the evaluation results.

Comparative Example 1 Polyethylene terephthalate having a weight average molecular weight of 36,000 containing 0.4 parts by weight of cohesive silica particles having an average particle diameter of 1.2 μm was crystallized and dried at 140 ° C. for 3 hours under reduced pressure. Then, using an extruder with a screw diameter of 45 mm, extruded at a T die die temperature of 270 ° C., and a diameter of 300 m
m to form an unstretched film. Then 3.8 mm in the longitudinal direction between 95 ° C. heating rolls.
After being stretched twice, it is sent to a tenter type stretching machine, stretched 4.0 times in the width direction at 98 ° C, and further stretched at 100 ° C in a tenter.
To produce a 2.0 μm thick film.
The crystal melting energy of the film was 48.0 J / g.

Next, the obtained film was bonded to Japanese paper made of 100% natural fiber made of manila hemp using vinyl acetate as an adhesive and having a basis weight of 12 g / m ² , and a silicone release agent was applied to the film surface. Then, a heat-sensitive stencil master was prepared and evaluated. Table 1 shows the evaluation results.

Comparative Example 2 Copolyester A of ethylene terephthalate and ethylene isophthalate having a weight average molecular weight of 32,000
(Copolymer molar ratio 78/22) was used as a raw material for the film, and a 2.0 μm-thick film was produced in the same manner as in Example 1 except for extruding at a T-die die temperature of 270 ° C. The crystal melting energy of the film was 18.7 J / g.

Next, the obtained film was bonded to a Japanese paper having a fiber weight of 12 g / m ² of 100% natural fiber made of Manila hemp using vinyl acetate as an adhesive and applying a silicone release agent to the film surface. Then, a heat-sensitive stencil master was prepared and evaluated. Table 1 shows the evaluation results.

Example 2 A D-lactic acid, L-lactic acid and 6-hydroxycaproic acid having a composition ratio of 80: 5: 15 and a weight average molecular weight of 150,000
A film having a thickness of 1.5 μm was prepared in the same manner as in Example 1 except that D-lactic acid polymer B of No. 0 was used. The crystal melting energy of the film was 30.5 J / g.

Next, the obtained film was bonded to a paper made of manila hemp as a raw material using vinyl acetate as an adhesive and Japanese paper having a fiber weight of 12 g / m ² , and a silicone release agent was applied to the film surface. Then, a heat-sensitive stencil master was prepared and evaluated. Table 1 shows the evaluation results.

Example 3 A film having a thickness of 1.5 μm was prepared in the same manner as described above, using a raw material obtained by kneading a D-lactic acid polymer A and a D-lactic acid polymer B at a blend ratio of 80:20 using a twin-screw extruder. did. The crystal melting energy of the film was 33.2 J / g.

Next, the obtained film was bonded to Japanese paper having a fiber weight of 12 g / m ² of 100% natural fiber made of Manila hemp using vinyl acetate as an adhesive and applying a silicone release agent to the film surface. Then, a heat-sensitive stencil master was prepared and evaluated. Table 1 shows the evaluation results.

Example 4 A 1.8 μm thick film was prepared in the same manner as described above, using a mixture obtained by kneading a copolyester A and a D-lactic acid polymer A at a blend ratio of 20:80 with a twin-screw extruder. . The crystal melting energy of the film was 22.6 J / g.

Next, the obtained film was bonded to a Japanese paper made of manila hemp as a raw material using vinyl acetate as an adhesive and having a fiber weight of 12 g / m ² , and a silicone release agent was applied to the film surface. Then, a heat-sensitive stencil master was prepared and evaluated. Table 1 shows the evaluation results.

Comparative Example 3 D-lactic acid polymer C100 having a weight-average molecular weight of 100,000 and a composition ratio of D-lactic acid and L-lactic acid of 55:45.
0.4 parts by weight of cohesive silica particles having an average particle size of 1.2 μm
After adding parts by weight and mixing, the mixture was supplied to a twin-screw extruder and extruded at 220 ° C. into pellets. A film having a thickness of 2.0 μm was prepared from the obtained pellets in the same manner as in Example 1. The crystal melting energy of the film was 20.3 J / g.

Next, the obtained film was bonded to Japanese paper having a fiber weight of 12 g / m ² of 100% of natural fibers made of manila hemp using vinyl acetate as an adhesive, and a silicone release agent was applied to the film surface. Then, a heat-sensitive stencil master was prepared and evaluated. Table 1 shows the evaluation results.

Example 5 Using a rectangular spinneret having a hole diameter of 0.35 mm and 100 holes, polyethylene terephthalate having a weight average molecular weight of 22,000 was spun out by melt blow at a die temperature of 290 ° C. and a discharge rate of 35 g / min. The fibers were collected on a conveyor, and calendered between metal rolls heated to 70 ° C. to produce an unstretched nonwoven fabric having a basis weight of 130 g / m ² .

In the same manner as in Example 1, poly-D-lactic acid A was added to 1
After drying at 20 ° C. under reduced pressure for 3 hours, using a 45 mm screw diameter extruder, extruded at a T die die temperature of 215 ° C.,
An unstretched film was produced by casting on a cooling drum having a diameter of 300 mm.

An unstretched nonwoven fabric was superimposed on the obtained unstretched film, supplied to a heating roll, and thermocompression-bonded at a roll temperature of 100 ° C. The laminate thus obtained was stretched 3.5 times in the length direction between heating rolls at 90 ° C., then fed into a tenter type stretching machine, stretched 4.0 times in the width direction at 93 ° C., and further in the tenter. A heat-sensitive stencil master having a thickness of 70 μm was prepared by heat treatment at 120 ° C. On the film surface of the master, a wax-based release agent was applied using a gravure coater at a weight of 0.1 g / m ² after drying at the entrance of the tenter. The fiber weight of the obtained master was 10 g /
m ² and average fiber diameter was 6 μm. The thickness of the film alone was 1.2 μm, and the crystal melting energy was 37.2 J /
g. Table 1 shows the evaluation results.

[0059]

[Table 1]

[0060]

By using a biaxially stretched film having a D-lactic acid polymer composition as a film, the problems of the prior art can be solved, the variation in perforation diameter is small, the perforation sensitivity and printability are excellent, A heat-sensitive stencil film and a heat-sensitive stencil master having excellent head perforation at low energy can be obtained.

Claims (5)

[Claims] 1. A heat-sensitive stencil printing film comprising a biaxially stretched film comprising a polymer mainly composed of polylactic acid, wherein the amount of D-lactic acid component in the polylactic acid is 70 mol% or more. 2. The film for heat-sensitive stencil printing according to claim 1, wherein the film has a thickness of 0.2 to 3 μm. 3. The film has a crystal melting energy of 20-5.
The heat-sensitive stencil film according to claim 1, wherein the film is 0 J / g. 4. A heat-sensitive stencil master comprising the film according to claim 1 and a porous support. 5. The heat-sensitive stencil printing master according to claim 4, wherein the film and the porous support are joined without using an adhesive.